Fix issue #568: Parse string 'expires' before encoding secure cookie.
Fix issue #568: Parse string 'expires' before encoding secure cookie.

The `\Slim\Http\Util::encodeSecureCookie` function requires the
expires parameter to be a int. A string typed 'expires' or
'cookie.lifetime' would pass a string in this case, which causes the
response cookie to be broken when parsed by `decodeSecureCookie`.

foxyantho/Slim